Know the pool size you want and how far the fixture sits? Find the beam angle — the optic — you need to buy. Adjust the sliders and the diagram shows the matching cone.
| Optic | Beam angle | Typical use |
|---|---|---|
| Narrow spot (NSP) | 8–15° | Artwork, columns, signage |
| Spot (SP) | 16–24° | Retail display, accents |
| Flood (NFL/MFL) | 25–40° | General accent, dining |
| Wide flood (WFL) | 45–60° | Ambient fill, wall wash |
| Very wide (VWFL) | 70°+ | Low ceilings, even fill |
Already know your beam angle and want the spread instead? Use the Beam Spread Calculator.
Worked example: to light a 1.2 m pool from 2.4 m away you need 2 × arctan(1.2 / 4.8) = 28° — a spot / narrow-flood optic.
Choosing narrow vs. wide. A narrow beam concentrates light into a tight, punchy pool — good for drawing the eye to one object, but it leaves the surrounding area dim. A wide beam spreads the same lumens over more area for even, general coverage, at the cost of that dramatic contrast. As a rule, go narrower for accent and feature lighting, wider for ambient fill.
Beam angle vs. mounting height. The same optic throws a smaller, brighter pool when mounted low and a larger, dimmer one when mounted high — beam angle sets the shape of the cone, distance sets its size. If you’re deciding between two fixtures with different beam angles, use this calculator at your actual ceiling height rather than comparing angles alone.
Common mistake. Edge falloff is gradual, not a hard line — the calculator gives the angle where output drops to about half-intensity, so the visible pool on a wall or floor is usually a bit larger (and dimmer at the rim) than the number suggests. For layered lighting, combining a narrow spot with a wider flood on the same object often reads better than one fixture trying to do both jobs.